This application is related to co-pending U.S. patent application Ser. No. 194,193, filed Feb. 25, 1980, now U.S. Pat. No. 4,288,710, the disclosure of which is incorporated by reference.
This invention relates to a system for measuring the base power and the radius of the base curve of an optical lens by determining the best focus of the lens.
Generally, it has been desirable to provide an accurate measurement of the various characteristics of optical lenses. Various prior art systems have taken advantage of electronic components in order to automatically perform a variety of tests on lenses. In one approach, a light beam source is scanned in a predetermined locus in the plane of the optical system. Refractive properties of the optical system under test are determined in relation to the instantaneous relative position at which the refracted light beam strikes a position-sensitive photoelectric surface. Another system measures a variety of lens characteristics by shifting the position of a phot-detector in the focal plane of the lens system, until the scanning light beam becomes centered on the detector, providing a zero output from the detector. Again, the light beam is scanned across the surface of the test lens to provide a measurement of refractive power. A common failing of the prior art systems is that the angle of refraction varies with the varying position of the light beam due to the relative motion between the light beam, the test lens, and the photo-detector. They simply detect the intensity of the refracted light beam as it varies with the angle of refraction. Further, this intensity signal depends upon a determination of the position at which the refracted light beam strikes the photo-detector. Thus, the need for scanning the light beam through a locus of positions may produce undesirable signal variations in accordance with the varying angles of refraction of the light beam by the test lens.